The head of London's police force says as many as five terror plots were foiled this year, as he warned of increasing pressure on resources amid the rising threat.

Metropolitan Police Commissioner Bernard Hogan-Howe told the BBC on Sunday that normally security services disrupt one plot annually. However, he says this year alone authorities have disrupted "we think four or five".

The Scotland Yard chief says police are increasingly worried about the possibility of a "lone wolf" attack and that thwarting such attacks was putting pressure on resources because police needed to move fast.

Hogan-Howe's comments came as Home Secretary Theresa May said she would propose a bill in the House of Commons this week forcing internet firms to retain data linking Internet Protocol or IP addresses to individual users.